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Chapter 4
Hydraulic Pumps
Hydraulic Pumps • Hydraulic Pump
Types
Chapter 4 — Hydraulic Pumps
The two main types of hydraulic pumps are positivedisplacement pumps and dynamic pumps.
Chapter 4 — Hydraulic Pumps
The two main types of prime movers used in fluid
power systems are electric motors or internal
combustion engines.
Chapter 4 — Hydraulic Pumps
Gallons per minute is the number of gallons a pump
can force into the system every minute and thus the
amount of fluid flow that pump can produce.
Chapter 4 — Hydraulic Pumps
Volumetric efficiency is the relationship between actual
and theoretical fluid flow of the pump.
Chapter 4 — Hydraulic Pumps
A typical application for a positive-displacement pump
includes the fluid power systems on a hydraulic
production press.
Chapter 4 — Hydraulic Pumps
Fixed-displacement
pumps are available
in various sizes with
different
displacement ratings.
Chapter 4 — Hydraulic Pumps
Typical applications for variable-displacement pumps
include systems that operate with varied system fluid
flow, such as industrial robots.
Chapter 4 — Hydraulic Pumps
All positive-displacement
pumps follow the same
basic operational steps to
create fluid flow.
Chapter 4 — Hydraulic Pumps
A gear pump consists of
various types of
meshing gears.
Chapter 4 — Hydraulic Pumps
An external gear pump consists of meshing gears
that form a seal with the pump housing and operates
similar to the four basic steps of a positivedisplacement pump.
Chapter 4 — Hydraulic Pumps
A lobe pump has two external-driven gears and
operates similar to an external gear pump.
Chapter 4 — Hydraulic Pumps
An internal gear pump
consists of a small
external drive gear
mounted inside a large
internal gear.
Chapter 4 — Hydraulic Pumps
Gerotor pump operation
is similar to internal gear
pump operation, with the
inner rotor having one
less gear tooth than the
outer rotor.
Chapter 4 — Hydraulic Pumps
Gear pump manufacturers typically provide assembly
diagrams for each specific pump.
Chapter 4 — Hydraulic Pumps
A vane pump contains
vanes in an offset rotor
and rotates the rotor to
produce the flow of
hydraulic fluid.
Chapter 4 — Hydraulic Pumps
Unbalanced vane pumps
operate similar to the four
basic steps of a positivedisplacement pump.
Chapter 4 — Hydraulic Pumps
A variable-displacement,
pressure-compensated
vane pump is a pump
that automatically adjusts
the amount of volume it
displaces per rotation by
centering the rotor when
the pressure in the
system starts to build.
Chapter 4 — Hydraulic Pumps
A balanced vane pump has two inlets and outlets at
opposite sides of the pump and contains an elliptical
cam ring.
Chapter 4 — Hydraulic Pumps
A cartridge assembly is located in a vane pump and
houses the vanes, rotor, and cam ring, which are all
placed between two plates.
Chapter 4 — Hydraulic Pumps
Vane pump manufacturers typically provide assembly
diagrams for each specific pump.
Chapter 4 — Hydraulic Pumps
Axial piston pumps consist of a number of pistons, a
piston block, piston shoes, a swash plate, and a shaft
and operate with four basic steps.
Chapter 4 — Hydraulic Pumps
A variable-displacement
piston pump has a swash
plate at an angle that can
be varied, thereby
varying the amount of
fluid flow (gpm).
Chapter 4 — Hydraulic Pumps
Bent-axis piston pumps operate in the same manner
as an axial piston pump, but rather than the swash
plate being at an angle, the pistons and piston block
are at an angle.
Chapter 4 — Hydraulic Pumps
Radial piston pumps
consist of reciprocating
pistons in cylinders and
can be classified as cam
or rotating piston pumps.
Chapter 4 — Hydraulic Pumps
Cavitation occurs as gas bubbles expand in a vacuum
and implode when entering a pressurized area.
Chapter 4 — Hydraulic Pumps
Hydraulic pumps are available in both double and
triple pump designs
Chapter 4 — Hydraulic Pumps
Hydraulic pump schematic symbols are used to
determine general information about the type of pump
used in a system.